neon oscilators ? and the Trautonium

[Peter Blackett]

Hi,
following on from the recent posta about the subject .
anyone know where I might find more info on Neon oscilators and their
design ?
[think they might be called relaxation oscilators ? ].
Be interested to know any advantages / disadvantages for use at Audio
and LF frequencies .
Didn't some early electronic instruments use them ?
the Trautonium ? made by Telefunken 
regards Peter
South London England